It is known from the related art, as represented by European Patent No. 0 001,298 (corresponding to U.S. Pat. No. 4,228,700), that when changing gears with an automatic multi-step reduction gear, the respective gear shift valves can be driven as a function of whether the engine is in pushing (coasting) or pulling (traction) operation. By linking a pushing or pulling operation detected with the type of gear shifting (upshifting or downshifting), a gear shifting strategy can be selected to permit the most comfortable and gear-protective adjustment of engine speed to the new gear. In particular, the intent is for the shifting of the required gear shift valves at the start of the shifting operation to take place with a positive overlap, namely at the start of the shifting sequence in power upshifting and in pushing downshifting and at the end of the shifting sequence in pushing upshifting and power downshifting.
German Patent Application No. 42 32 974 (corresponds to British Patent No. 2,271,198) and German Patent Application No. 42 39 711 discribe a model for calculating the indexed engine torque as a function of engine speed, engine load, firing angle, ignition blanking stages and of loss torque as a function of engine speed, engine load, engine temperature and consumers (e.g., a.c. compressor). In German Patent Application No. 44 07 475, this engine torque model for calculating the indexed engine torque is supplemented by the lambda function, i.e., the dependence on the fuel-air ratio. These publications disclose the precise calculation of instantaneous engine output torque at each operating point.